The first time I ever woke up with my arm asleep in the middle of the night, I was scared shitless. I thought something had happened and my arm had died. I think we’ve all had that flood of relief as the sensation returns, despite the prickles that we know are supposed to follow. I still am always a bit worried that my arm won’t work out.
Though it always has to date, there is the chance that something could happen in the future where it wouldn’t. Whether a severed spinal cord or some other traumatic injury, there are plenty of people out there who have lost the use of their limbs.
Luckily, there are people like postdoc Christian Ethier and graduate student Emily Oby out there working on a solution. And in a paper just published in Nature, the Northwestern University duo demonstrate the ability to return use of a limb to monkey using nothing but their brainwaves.
Functional electrical stimulation (FES) is not a new technology. It uses electrodes to directly stimulate muscles. However, previous systems rely on other working muscles to provide the input. For example, a shrug of the shoulders might make a hand grasp on to something. But here, Ethier and Oby have bypassed the need for physical input by implanting a sensor in the brain that literally reads what the patient is thinking and transmits the signal to the arm.
It bypasses the spinal cord.
To do this, the team trained a rhesus monkey to grasp a blue ball and put it into a tube. They looked for the neural signals in the brain that were signaling the arm to complete the task. Of course, there are millions of neurons interacting behind the scenes, but the end result is a signal that is transmitted to the muscles by relatively few neurons. By looking at just 100, they could identify the correct pattern.
This was accomplished by embedding a small microchip into the monkeys’ brains; a chip that is already in use in other medical studies and widely available. Ethier and Oby then paralyzed the monkeys’ arms by injecting a temporary nerve blocker just past the elbow of the subjects.
I guess having them sleep on their arms took too long.
The monkeys were then instructed to pick up the ball and put it in the tube. Thanks to the microchip recognizing the commands, it was able to send signals directly to their arms and complete the instructions, despite the paralyzed forearm with an 80 to 90 percent success rate.
Of course, this is a relatively simple task that controlled just four muscles. More complicated tasks like brushing your teeth or even unlocking a door would require many more muscles and likely a more complex neural pattern to recognize. Additionally, in people who lost the use of their limbs long ago, the neurons used to control them could have been hijacked to perform other tasks and the muscles could have become much weaker.
But neurophysiologist Lee Miller, who runs the lab that the trials were conducted in, doesn’t think that will be a problem. He believes this basic knowledge – and that can be gleaned from other trials – will be enough to move the technology forward and perhaps one day restore much of the function to paralyzed limbs.
Only time will tell.